Pile driving hammers have been in use for many years for driving tubular pilings. Typically, pipe columns are assembled by on-site joining of pipe sections by welding. When welded casing came into use, the final end preparation was done on site and care in preserving a prepared end was not especially important. To the extent practical all pipe sections are now prepared in the shop. Shop preparation for serial welding of pipe sections into pipe strings involves cutting a bevel on each end of each pipe section, excepting the lower terminal. Joining of shop prepared pipe sections is a field operation involving a great deal of tied-up assets. Delays in the field for repair of damaged pipe ends is especially costly.
Hammering directly on the prepared end of the top pipe section will promptly damage the prepared profile and necessitate on-site repairs. The prepared end of the pipe section does have a flat area which is usually less than one fourth the radial dimension of the bevel. The use of a flat ended driving adapter as an insert between the top of the pipe and the hammer reduces the damage to the end of the pipe, and repair after driving is often unnecessary. The damage does, however, sometimes occur. Quite possibly some damage goes unnoticed and results in welding an impaired junction.
Two bevel angles are commonly found in current practice. Thirty degree and fifteen degree bevels, relative to a transverse plane, can be driven with the same adapter if the combined angles are situated to engage the different angles on areas where hammering causes no damage. A suitable combined angle on the driver places the engaged portion of the thirty degree angle to involve about two thirds of the radial dimension of the bevel near the pipe bore. The fifteen degree angle, then, is engaged by about one third of the bevel near the outer dimension. Any marring of the outer portion of the bevel is covered satisfactorily by the weld metal deposit and does not compromise joint quality. For the thirty degree bevel, the adapter bevel is more acute by about one degree to more lightly engage the pipe bevel surface near the bore to avoid deforming the bore.
Welding bevels are not always the same but their characteristics are known well in advance of on-site use. That provides opportunity to prepare a driving adapter that engages the pipe over a large area of the end profile, and surface combinations on the driving adapter, as stated above, can be devised.
It is therefore an object of this invention to provide a pipe driving adapter for use between the top end of a pipe column and the pile driving hammer that is shaped to engage the general profile of the end surface of the pipe.
These and other objects, advantages, and features of this invention will be apparent to those skilled in the art from a consideration of this specification, including the attached claims and appended drawings.